rustc_attr_parsing/
validate_attr.rs

1//! Meta-syntax validation logic of attributes for post-expansion.
2
3use std::convert::identity;
4use std::slice;
5
6use rustc_ast::token::Delimiter;
7use rustc_ast::tokenstream::DelimSpan;
8use rustc_ast::{
9    self as ast, AttrArgs, AttrKind, Attribute, DelimArgs, MetaItem, MetaItemInner, MetaItemKind,
10    Safety,
11};
12use rustc_attr_ir::AttrPath;
13use rustc_errors::{Applicability, Diagnostic, PResult};
14use rustc_feature::BUILTIN_ATTRIBUTE_SET;
15use rustc_lint_defs::builtin::ILL_FORMED_ATTRIBUTE_INPUT;
16use rustc_parse::parse_in;
17use rustc_session::diagnostics::report_lit_error;
18use rustc_session::parse::ParseSess;
19use rustc_span::{Span, Symbol, sym};
20
21use crate::{AttributeParser, AttributeTemplate, diagnostics as errors, template};
22
23pub fn check_attr(psess: &ParseSess, attr: &Attribute) {
24    use ast::SyntheticAttr::*;
25    match &attr.kind {
26        AttrKind::Normal(_) => {}
27        AttrKind::Synthetic(CfgTrace(_) | CfgAttrTrace(_))
28        | AttrKind::DocComment(..)
29        | AttrKind::Generated(..) => return,
30    }
31
32    let builtin_attr_info = attr.name().and_then(|name| BUILTIN_ATTRIBUTE_SET.get(&name));
33
34    // Check input tokens for built-in and key-value attributes.
35    if let Some(name) = builtin_attr_info {
36        if AttributeParser::is_parsed_attribute(slice::from_ref(name)) {
37            return;
38        }
39        match parse_meta(psess, attr) {
40            // Don't check safety again, we just did that
41            Ok(meta) => {
42                // FIXME The only unparsed builtin attributes that are left are the lint attributes, so we can hardcode the template here
43                let lint_attrs = [sym::forbid, sym::allow, sym::warn, sym::deny, sym::expect];
44                if !lint_attrs.contains(name) {
    ::core::panicking::panic("assertion failed: lint_attrs.contains(name)")
};assert!(lint_attrs.contains(name));
45
46                let template = crate::AttributeTemplate {
    word: false,
    list: Some(&["lint1", "lint1, lint2, ...",
                    r#"lint1, lint2, lint3, reason = "...""#]),
    one_of: &[],
    name_value_str: None,
    docs: Some("https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"),
}template!(
47                    List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
48                    "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
49                );
50                check_builtin_meta_item(psess, &meta, attr.style, *name, template, false)
51            }
52            Err(err) => {
53                err.emit();
54            }
55        }
56    } else {
57        let attr_item = attr.get_normal_item();
58        if let AttrArgs::Eq { .. } = attr_item.args {
59            // All key-value attributes are restricted to meta-item syntax.
60            match parse_meta(psess, attr) {
61                Ok(_) => {}
62                Err(err) => {
63                    err.emit();
64                }
65            }
66        }
67    }
68}
69
70pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, MetaItem> {
71    let item = attr.get_normal_item();
72    Ok(MetaItem {
73        unsafety: item.unsafety,
74        span: attr.span,
75        path: item.path.clone(),
76        kind: match &item.args {
77            AttrArgs::Empty => MetaItemKind::Word,
78            AttrArgs::Delimited(DelimArgs { dspan, delim, tokens }) => {
79                check_meta_bad_delim(psess, *dspan, *delim);
80                let nmis =
81                    parse_in(psess, tokens.clone(), "meta list", |p| p.parse_meta_seq_top())?;
82                MetaItemKind::List(nmis)
83            }
84            AttrArgs::Eq { expr, .. } => {
85                if let ast::ExprKind::Lit(token_lit) = expr.kind {
86                    let res = ast::MetaItemLit::from_token_lit(token_lit, expr.span);
87
88                    match res {
89                        Ok(lit) => {
90                            if token_lit.suffix.is_some() {
91                                let mut err = psess.dcx().struct_span_err(
92                                    expr.span,
93                                    "suffixed literals are not allowed in attributes",
94                                );
95                                err.help(
96                                    "instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), \
97                                    use an unsuffixed version (`1`, `1.0`, etc.)",
98                                );
99                                return Err(err);
100                            }
101                            MetaItemKind::NameValue(lit)
102                        }
103                        Err(err) => {
104                            let guar = report_lit_error(psess, err, token_lit, expr.span);
105                            let lit = ast::MetaItemLit {
106                                symbol: token_lit.symbol,
107                                suffix: token_lit.suffix,
108                                kind: ast::LitKind::Err(guar),
109                                span: expr.span,
110                            };
111                            MetaItemKind::NameValue(lit)
112                        }
113                    }
114                } else {
115                    // Example cases:
116                    // - `#[foo = 1+1]`: results in `ast::ExprKind::Binary`.
117                    // - `#[foo = include_str!("nonexistent-file.rs")]`:
118                    //   results in `ast::ExprKind::Err`. In that case we delay
119                    //   the error because an earlier error will have already
120                    //   been reported.
121                    let msg = "attribute value must be a literal";
122                    let mut err = psess.dcx().struct_span_err(expr.span, msg);
123                    if let ast::ExprKind::Err(_) = expr.kind {
124                        err.downgrade_to_delayed_bug();
125                    }
126                    return Err(err);
127                }
128            }
129        },
130    })
131}
132
133fn check_meta_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
134    if let Delimiter::Parenthesis = delim {
135        return;
136    }
137    psess.dcx().emit_err(errors::MetaBadDelim {
138        span: span.entire(),
139        sugg: errors::MetaBadDelimSugg { open: span.open, close: span.close },
140    });
141}
142
143/// Checks that the given meta-item is compatible with this `AttributeTemplate`.
144fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaItemKind) -> bool {
145    let is_one_allowed_subword = |items: &[MetaItemInner]| match items {
146        [item] => item.is_word() && template.one_of.iter().any(|&word| item.has_name(word)),
147        _ => false,
148    };
149    match meta {
150        MetaItemKind::Word => template.word,
151        MetaItemKind::List(items) => template.list.is_some() || is_one_allowed_subword(items),
152        MetaItemKind::NameValue(lit) if lit.kind.is_str() => template.name_value_str.is_some(),
153        MetaItemKind::NameValue(..) => false,
154    }
155}
156
157pub fn check_builtin_meta_item(
158    psess: &ParseSess,
159    meta: &MetaItem,
160    style: ast::AttrStyle,
161    name: Symbol,
162    template: AttributeTemplate,
163    deny_unsafety: bool,
164) {
165    if !is_attr_template_compatible(&template, &meta.kind) {
166        // attrs with new parsers are locally validated so excluded here
167        emit_malformed_attribute(psess, style, meta.span, name, template);
168    }
169
170    if deny_unsafety && let Safety::Unsafe(unsafe_span) = meta.unsafety {
171        psess.dcx().emit_err(errors::InvalidAttrUnsafe {
172            span: unsafe_span,
173            name: AttrPath::from_ast(&meta.path, identity),
174        });
175    }
176}
177
178pub fn emit_malformed_attribute(
179    psess: &ParseSess,
180    style: ast::AttrStyle,
181    span: Span,
182    name: Symbol,
183    template: AttributeTemplate,
184) {
185    // Some of previously accepted forms were used in practice,
186    // report them as warnings for now.
187    let should_warn = |name| #[allow(non_exhaustive_omitted_patterns)] match name {
    sym::doc | sym::link | sym::test | sym::bench => true,
    _ => false,
}matches!(name, sym::doc | sym::link | sym::test | sym::bench);
188
189    let error_msg = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("malformed `{0}` attribute input",
                name))
    })format!("malformed `{name}` attribute input");
190    let mut suggestions = ::alloc::vec::Vec::new()vec![];
191    let inner = if style == ast::AttrStyle::Inner { "!" } else { "" };
192    if template.word {
193        suggestions.push(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1}]", inner, name))
    })format!("#{inner}[{name}]"));
194    }
195    if let Some(descr) = template.list {
196        for descr in descr {
197            suggestions.push(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1}({2})]", inner, name,
                descr))
    })format!("#{inner}[{name}({descr})]"));
198        }
199    }
200    suggestions.extend(template.one_of.iter().map(|&word| ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1}({2})]", inner, name,
                word))
    })format!("#{inner}[{name}({word})]")));
201    if let Some(descr) = template.name_value_str {
202        for descr in descr {
203            suggestions.push(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1} = \"{2}\"]", inner, name,
                descr))
    })format!("#{inner}[{name} = \"{descr}\"]"));
204        }
205    }
206    // If there are too many suggestions, better remove all of them as it's just noise at this
207    // point.
208    if suggestions.len() > 3 {
209        suggestions.clear();
210    }
211    if should_warn(name) {
212        let suggestions = suggestions.clone();
213        psess.dyn_buffer_lint(
214            ILL_FORMED_ATTRIBUTE_INPUT,
215            span,
216            ast::CRATE_NODE_ID,
217            move |dcx, level| {
218                crate::diagnostics::IllFormedAttributeInput::new(&suggestions, template.docs, None)
219                    .into_diag(dcx, level)
220            },
221        );
222    } else {
223        suggestions.sort();
224        let mut err = psess.dcx().struct_span_err(span, error_msg).with_span_suggestions(
225            span,
226            if suggestions.len() == 1 {
227                "must be of the form"
228            } else {
229                "the following are the possible correct uses"
230            },
231            suggestions,
232            Applicability::HasPlaceholders,
233        );
234        if let Some(link) = template.docs {
235            err.note(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("for more information, visit <{0}>",
                link))
    })format!("for more information, visit <{link}>"));
236        }
237        err.emit();
238    }
239}
rustc_attr_parsing/validate_attr.rs

rustc_attr_parsing/
validate_attr.rs
